keep causing a skip or lugging code P0171

ok u have totally lost me now. i have no clue on what any of those procedures r or how to perform them. i dont even know what dtc"s are or koer self test or how to do any of that can you plz put that into laymans terms so that any idiot can do it or is their no help for my problem ? can any1 help me out there. i was involved in an accident with my wifes car yesterday and now this truck is the only way for my family to get around now and last time this happened my engine blew before i figured out was wrong. some1 plzzzzzzzzzzzzhelp me

Make sure there is power to it. Let me know what happens.

Joe

Okay..basically you need to inspect visually, as well as with a meter, all your wiring to the main computer as well as the wires to the sensors (MAF, EGR etc..).

Ok so I went to Pep-Boys today and picked up a new BWD injector for cylinder 1. They were $10 cheaper than at Advance! I pulled out my toolbox right there in the parking lot and did the swap. Disconnected the battery prior to discharge any run-setting the computer may have stored for the misfire/lean condition. Cussed under my breath when the new injector wouldn't fit. Then found the old o-ring from the old injector was stuck inside the fuel rail blocking the new one. So I removed the o-ring, slapped in the new injector and fired it up. The "lub-dub" lope is still there sometimes at idle, but when I pulled out from the light it was as different as going from the stock gears to 4.10s!!! My truck has it's power back!!! (I think!) I cleared the code and I'm going to log some miles tomorrow to see if a code will show up again. I'm going to go ahead and order a complete set of rebuilt injectors for $100 and swap the rest out. The loping at idle I think may still be from the dpfe sensor. I'm going to pull the throttle body soon and go through the ports on the (3-year old) EGR and vacuum lines soon.

ok i jut remembered that i broke the wires off under the plentum connected to the knock sensor i believe. there is a sensor under the plentum dead center under plentum, on top, in middle of the block. not the heat sensor on the bank 1 head under plentum but dead center where u cant reach unless u take plentum back off wires r connected to harness but not to sensor and they r bare would or could that be the problem? just remember that the block and heads in truck now are from the 2000 grand marquis not the original f-150 block and heads, and the 2000 engine had no knock sensor in it where the f-150 4.6 did and has it in the wire harness where the 2000 harness doesnt so i put one in but i broke the sensor tightening it and broke the wires off and they r bare under the plentum probably touching the head,plentum or block arching or does it do that? awaiting the answer to this one asap plz

I hope that takes care of it. Keep me up to date.

Joe

Well that sounds very dangerous and I'm sure it is causing an issue. No for sure way to tell if that is the exact cause of the problem you have without fixing it really.

Ok- so I logged about 200 miles on my truck last night and finally got to some hills where I noticed the power still wasn't where it should be. Soon the check engine light came on and now I'm back to square one. I'm going to scan it again. I'm assuming it's still the p0171 code, so should I be looking at replacing the DPFE now?

i also found out today that the kock sensor only works when needed so it is very obsolite it only works when the engine is knocking ,which it is not is this true? 62 dollars for this useless part and 3 hrs labor to replace is it worth it? down the road i will replace it but cant afford the waste of time or money right now ? should i just bring this to ford or a garage with a scan computer or keep plugging away

I would have it checked first.

The knock sensor allows the engine to run with the ignition timing as far advanced as possible. The computer will continue to advance the timing until the knock sensor detects pinging. At that point the computer retards the ignition timing just enough for the pinging to stop. So technically yes, it only works when it needs to stop a knocking/pinging issue. A diagnostic test at a dealer may be cheaper in the long run than continously replacing part after part getting nowhere. I would check that fuel pressure out before taking in to the dealer though..may just be the regulator after all ?




Thanks for using 2CarPros.com!

Well I guess I'm taking my truck back to the dealer to have them reanalyze everything tomorrow. I'm just exhausted from playing the "that didn't work, try replacing this" game. I'm dying to see how this new motor will run when it's actually running on all 8 cylinders!

i stil believe the vacume lines r wrong or should be routed differently to work properly. what do u think?

Let me know what you find.

Yeah it definitely seems like somethign is hooked up a little screwy than it should be.. the only vacuum diagram i can find is the one below

that is the f150 engine. what size was the engine you replaced it with ?

I had to go out of town for a few days so I dropped my truck back off at the dealer on monday, and got a rental for my trip. I came back late wednesday and talked to the same mechanic that originally worked on my truck pre-new-engine. He was completely puzzled. He had pulled and checked everything possible. Sprayed parts cleaner on everything imaginable, and still had no rpm revs. The fuel trim levels are high on BOTH banks, though Bank 1 was the only one kicking the code. Trim levels were around 25-27% on both banks, he said they should be somewhere around 12-15% I think and fuel pressure was within spec all the way around. He was going to look further into it today but I had to have it to get to work. They did not charge me this time since nothing was found and he said he wasn't throwing in the towel yet. Is there any canisters or hidden plastic intake pieces I should check for split/pitted seams? The PCV and hoses were inspected, blocked, and ruled out. EGR is operating properly, so it's not the DPFE. IAC is operating properly. Does ANYone have ANY ideas before I take it back, AGAIN?

i also have that diagram and i have no idea what the things r other than a few of the obvious, egr , throtle body canister which i do not have or is missing but was never on there. i need a more step by step one to know for sure. i have one going from brake booster or behind master cylinder to to top of throttle body then i have pcv valve on bank 1 side valve cover to rear of throttle body, then i have 1 from bank 2 side of valve cover to intake tube near throttle body but on 4" intake tube front of throttle body then i have small tubes from egr and fuel pressure gauge to bottom of thing on rear wall next to master cylinder then to another thing that looks like that to bank 1 side of throttle body. then to two small conectors behind the battery where harness begins,then down to side of transmission with two small tubes, but no canister as far as i can see ok

I'm sorry to hear you're still having trouble. I have to admit, this is a difficult one. The interesting part is the #1 cylender is and has been the problem since the original engine. Something tells me it has to deal with something simple that is being overlooked. I would suggest giving them one more chance. If it still is pertaining to #1 only, we will start over with the basics.

i have a friend that used to work for ford and he thinks that i should ground the block to body two more times then ground the intake to the head to the block to the body then he wants me to change the injectors that dont work when the vacume lines r connected and see if the injectors were bad or the fuel rail he wants me to blow high pressure air through them to see if there is any blockage going on. and he try to see if it runs any better . i was wondering if u read that i did a node test and i metered test and all 8 injectors were the same, 13.8 volts and all blinked the same speed and brightness. so i will do the 60 second pressure test and let you know the outcome tomorrow.what a pain in the ass this is becoming, but i almost can see the light from when i first took the first bolt out of the old engine to start taking it out to replace. but i will tell you i will have learned quite a bit during this process. lol

Ok, so I am getting ready to completely strip down my truck, sell it piece by piece, and use the money for a down payment on a new one. The more and more I talked to people, the more it seemed the computer was the only thing I had not replaced and was something that could cause the power loss and lean condition. I ordered a remanufactured brainbox from Adv Auto Parts that was pre-flashed at the factory. I pulled the harness, no burn marks or corrosion, sprayed in some electrical cleaner, and dielectric greased the connection. I said a few prayers and took it down the road, nothing. Absolutely no change. I dropped it off tonight with one last mechanic. This is seriously my last move. If he cannot find it, you will find the new motor, tranny, fabtech lift, wheels/tires, winch bumper and all the other good parts on ebay and craigslist next week. PLEASE HELP ONE LAST CHANCE!!!

Have you tried just listening to the injectors? listen for a clicking sound coming from the injectors while the engine is running by using a mechanic's stethoscope, or a long screwdriver.

o ok then nevermind my last post then. injector circuit is good then. yeah im not sure if just one ground is really enough there.

ok i went out and replaced 1 injector and it did nothing. then i blew out the lines and it also did nothing. then i did the pressure check and it started out @ 26 lbs of pressure then it slowly went to 36 lbs of pressure then stayed there for the 60 seconds plus i kept it on there for an additional 60 seconds. now what???? i was for sure it was an injector. but what the hell do i know.

im going out now to ground the piss out of the engine and see if that works.

Ok I really thought it was with the injectors but we are going to have to go further down the fuel circuitry than that. Next we will need to test the PCM. Do this by turning ignition OFF and connecting PCM to the breakout box. Connect non-powered 12-volt test light between each injector ( 1 at a time ) and test pins Number 71 and 97. Crank or start the engine. If the light glows dimly then the PCM is ok and we will go on further with diagnosis. If the test light does not glow dimly (no light/ bright light) then the PCM needs replaced.

i think i messed up. i connected the test light to a ground and touched pcm wires # 71 and 97 but i only turned 0n the key. i did not turn over i did not understand until i read the paragraph again is that ok or do i have to crank over? by the way the light was very bright during that test, same brightness as conected to the battery with test light. but i will go try test again the right way now brb.

need to crank or start engine

ok i did the test the correct way now and light did dim on all injectors on 71 and 97 pins. @ injector site and on pcm site.

Ok then this rules out your PCM AND your fuel injectors so it must be in the air induction. i may have already said this or you may have already done these but i can't remember so check the PCV system for leaks or restrictions, check all vacuum hoses for damage and tight connections.

i did replace the pcv as a precaution ,cheap enough, but it did no good. now if u remember from a previous message. i said when i take a vacume line off on bank 1 side of throttle body ,the injectors that were working, stop and the injectors that didn't work, start to work but engine idle fluctuates up and down alot when i do this. i just cant get all injectors to work @ once. weird huh. what do i do from here. i've had it with this problem i just need my truck to work. i also replaced all vacume lines.

1997 Ford F150 po171 code

A code P0171 or P0174 indicate the engine is running lean. This means there is too much air and/or not enough fuel. You can confirm the engine is running lean by looking at Short Term Fuel Trim (STFT) and Long Term Fuel Trim (LTFT). Normally, STFT and LTFT should be plus or minus 8 from zero. If STFT and/or LTFT are more than about +10 or higher, it indicates the engine is running LEAN. Negative numbers (-10 or more) indicates the engine is running RICH.

A lean fuel condition can be caused by:

* Low fuel pressure due to a weak pump or leaky fuel pressure regulator. (use a fuel pressure gauge to check fuel pressure at idle)

* Dirty fuel injectors. (try cleaning the injectors)

* Vacuum leaks at the intake manifold, vacuum hose connections or throttle body. (Use a vacuum gauge to check for low intake vacuum)

* Leaky EGR valve. (Check operation of EGR valve)

* Leaky PCV Valve or hose. (Check valve and hose connections)

* Dirty or defective Mass Airflow Sensor (MAF). (Try cleaning the MAF sensor wires or filament with aerosol electronics cleaner. Do NOT use anything else to clean the sensor, and do not touch the sensor wires)

* TIP: On many Fords, a P0171 and/or P0174 Lean Code may sometimes appear because of a bad Differential Pressure Sensor (DPFE). This sensor monitors EGR flow, and is located on the engine near the EGR valve. There are two hoses that connect the sensor to the tube that runs from the exhaust manifold to the EGR valve. The sensor misreads EGR flow and the computer increases EGR which has a leaning effect on the fuel mixture. The fix is to replace the DPFE sensor

i have tried all that u have written to me here and more. i replaced both the fuel pressure regulator and and that other thing that the egr is connected to the dpfe sensor. i have checked pressure stays steady @ 36 lbs for 2 minutes and more i checked the pcm for power, replaced the injectors. checked for proper voltage @ the injectors. blew out fuel rail , checking for blockage, replaced the coil paks a while ago.plugs, wires, replaced pcv. changed oil ,fuel and oil filter, replaced all vacume lines, checked for tightness, replaced just about everything i can reach and that i had from other motor that was good except for the knock sensor which is broke and disconnected under plentum w/ bare wires, but has nothing to do with fuel of air. i thik it is a vACUME leak. this happened to my previous engie also and i kept driving it and it blew a coil pak and 2 cylinders resulting i changing the motor so what ever it is or was is still there from previous engine. any other suggestions. i could really use an actual birds eye view of the engine vacume routing. please read all other messages before writing back so you can c what i have done ad eliminated so far. thanks for jumpin onboard rasmataz. i could use all the help i could with this one. oh and what do you think about the o2 sensors? could they be the problem? it's 100 dollars to find out as i think there r only 2 on this model or is there four.

Follow the link below to learn how to check an O2 sensor before replacing them..


https://www.2carpros.com/how_to/how_to_test_oxygen_sensor.htm

i will go out in the morning and sheck the 02 sensors any idea though what wire (color) is the sensing wire on the 02 sensor itself?

From: miamiii13
To: rasmataz
Posted: Mon Mar 16, 2009 10:30 pm
Subject: any other ideas
do u have any other suggestions to try or to eliminate things

Look for vacuum leaks and try the scantool for the trimmings this is as far as I can take you-Sorry

Sensing wire should be red/light green for your trucks O2 sensors

ok ty , i will test them at some point 2day.anything else i can try? any ideas yet, or r u stumped also ?

does anyone have any ideas or an fix for this troublesome problem with this truck ? i neeeeeeeeeeeeed help fast good weather is approaching and i need this truck for work to support my family. At this time this is our only vehicle as a result of an accident with my wifes car last week. someone pleeeeeeeeeeeeeeeeeeeeeeeeez help me.

is there a way to check that the fuel pump is putting out the correct pressure and operating the correct way?

i just disconnected a few of the plug wires from the coil pak and the engine did nothing. 2 from each coil pak did not change the tone of the engine, but two from each coil pak did. the same ones that the injectors are'nt working. i am going to change a plug or two and c if that changes anything. So in short injectors 1, 4, 6 & 7 don't work and 1 , 4 , 6 , & 7 plug wires don't change the tone of engine when disconnected. but all the rest of the injectors do work and when i disconnect the plug wires 2,3,5, & 8 from the coilpaks the engine does nothing. any ideas is this just because of the injectors just not working again? i am getting spark from both coils when i disconnect the wire.i can clearly c the spark from wire to coil pak and i see spark at the end of the wire to the plug.